1. Endocrine Glands Dr. M. Diamond

2. Thyroid Found at the base of the throat Consists of two lobes and a connecting isthmus Produces two hormones –Calcitonin Decreases blood calcium levels by causing its deposition on bone Antagonistic to parathyroid hormone –Thyroid hormone Major metabolic hormone Composed of two active iodine-containing hormones –Thyroxine (T 4 )—secreted by thyroid follicles –Triiodothyronine (T 3 )— conversion of T 4 at target tissues

3. Thyroid hormone disorders Goiters –Thyroid gland enlarges due to lack of iodine –Salt is iodized to prevent goiters Cretinism –Caused by hyposecretion of thyroxine –Results in dwarfism during childhood

4. More… Thyroid hormone disorders Myxedema –Caused by hypothyroidism in adults –Results in physical and mental sluggishness Graves’ disease –Caused by hyperthyroidism –Results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, and exophthalmos (bug eyes)

5. Parathyroids Tiny masses on the posterior of the thyroid Secrete parathyroid hormone (PTH) –Stimulate osteoclasts to remove calcium from bone –Stimulate the kidneys and intestine to absorb more calcium –Raise calcium levels in the blood

6. Regulation of Calcium Level in Blood

7. Adrenals Sit on top of the kidneys Two regions –Adrenal cortex—outer glandular region has three layers Mineralocorticoids secreting area Glucocorticoids secreting area Sex hormones secreting area –Adrenal medulla—inner neural tissue region

8. Hormones of the adrenal cortex Mineralocorticoids (mainly aldosterone) –Produced in outer adrenal cortex –Regulate mineral content in blood –Regulate water and electrolyte balance –Target organ is the kidney –Production stimulated by renin and aldosterone –Production inhibited by atrial natriuretic peptide (ANP) Glucocorticoids (including cortisone and cortisol) –Produced in the middle layer of the adrenal cortex –Promote normal cell metabolism –Help resist long-term stressors –Released in response to increased blood levels of ACTH

9. Hormones of the adrenal cortex

10. Stress Response Hypothalamus and Adrenals Short termMore prolonged Stress Hypothalamus Nerve impulses Adrenal cortex Releasing hormone Corticotropic cells of anterior pituitary ACTH MineralocorticoidsGlucocorticoids 1.Retention of sodium and water by kidneys 2.Increased blood volume and blood pressure 1. Proteins and fats converted to glucose or broken down for energy 2. Increased blood sugar 3. Suppression of immune system Long-term stress response Short-term stress response Spinal cord Adrenal medulla Preganglionic sympathetic fibers Catecholamines (epinephrine and norepinephrine) 1. Increased heart rate 2. Increased blood pressure 3. Liver converts glycogen to glucose and releases glucose to blood 4. Dilation of bronchioles 5. Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity 6. Increased metabolic rate

11. More…. Adrenal cortex Sex hormones –Produced in the inner layer of the adrenal cortex –Small amounts are made throughout life –Mostly androgens (male sex hormones) are made but some estrogens (female sex hormones) are also formed

12. Adrenal cortex disorders Addison’s disease –Results from hyposecretion of all adrenal cortex hormones –Bronze skin tone, muscles are weak, burnout, susceptibility to infection –JFK Hyperaldosteronism –May result from an ACTH- releasing tumor –Excess water and sodium are retained leading to high blood pressure and edema

13. More… Adrenal cortex disorders Cushing’s syndrome –Results from a tumor in the middle cortical area of the adrenal cortex –“Moon face,” “buffalo hump” on the upper back, high blood pressure, hyperglycemia, weakening of bones, depression Masculinization –Results from hypersecretion of sex hormones –Beard and male distribution of hair growth

14. Hormones of the Adrenal medulla Produces two similar hormones (catecholamines) –Epinephrine (adrenaline) –Norepinephrine (noradrenaline) These hormones prepare the body to deal with short-term stress (“fight or flight”) by –Increasing heart rate, blood pressure, blood glucose levels –Dilating small passageways of lungs

15. Pancreas The pancreas is a mixed gland and has both endocrine and exocrine functions The pancreatic islets produce hormones –Insulin—allows glucose to cross plasma membranes into cells from beta cells –Glucagon—allows glucose to enter the blood from alpha cells –These hormones are antagonists that maintain blood sugar homeostasis

16. Regulation of blood glucose levels

17. Pineal Gland Found on the third ventricle of the brain Secretes melatonin –Helps establish the body’s wake and sleep cycles –Believed to coordinate the hormones of fertility in humans

18. Thymus Located posterior to the sternum Largest in infants and children Produces thymosin –Matures some types of white blood cells –Important in developing the immune system

19. Gonads Ovaries –Produce eggs –Produce two groups of steroid hormone Estrogens Progesterone Testes –Produce sperm –Produce androgens, such as testosterone

20. Ovaries Estrogens –Stimulate the development of secondary female characteristics –Mature female reproductive organs With progesterone, estrogens also –Promote breast development –Regulate menstrual cycle Progesterone –Acts with estrogen to bring about the menstrual cycle –Helps in the implantation of an embryo in the uterus –Helps prepare breasts for lactation

21. Testes Produce several androgens Testosterone is the most important androgen –Responsible for adult male secondary sex characteristics –Promotes growth and maturation of male reproductive system –Required for sperm cell production

22. Other Hormone-Producing Tissues and Organs Parts of the small intestine Parts of the stomach Kidneys Heart Many other areas have scattered endocrine cells

23. Placental hormones Produces hormones that maintain the pregnancy Some hormones play a part in the delivery of the baby Produces human chorionic gonadotropin (hCG) in addition to estrogen, progesterone, and other hormones